As Britain's youngest, shortest and lightest Olympic athlete, Rebecca Tunney is already used to superlatives. But on 29 July, vital statistics will matter no longer as she contemplates the balance beam at the North Greenwich Arena, and begins her quest for five artistic gymnastics medals.

Tunney, the 2012 British champion, will be performing in front of 20,000 spectators, the biggest crowd of her life, but she will be undaunted. "She takes everything in her stride. She's used to big occasions and she will treat it as just another competition. She knows that she has to be ready to deliver the routine to the best of her ability," said Claire Duffy, who has coached her for five years.

Tunney is 15 years and eight months, 4ft 9ins and 5st 7lb, but her diminutive statistics bear no relation to her determination nor the sacrifices she has made to get to London 2012. "It's been worth it. This is the best experience of my life. Not many people can say they've been to an Olympics at the age of 15 so it is an achievement," she said.

Tunney and four team-mates in Britain's squad will compete in the balance beam, vault, uneven bars, floor and team events. China dominated the gymnastic medals at Beijing but the British team hope home advantage will have as strong an effect as it did for China.

In the stands at the venue (formerly the Dome), Duffy will be watching nervously. "I will be a little bit anxious because I am not by her side, but also quietly confident. She has done all her preparation really well. On the day you never know what could happen," said Duffy.

Tunney's schedule is demanding. In addition to almost a full school week, she travels for 10 hours to and from her gym and trains for 32 hours every week. On Monday and Friday, she leaves school at lunchtime to go from Manchester to the City of Liverpool gymnastic club for a seven-hour session.

Like many teens, she is a keen tweeter but it's clear her life revolves around gymnastics. Her tweets tend to say she is on her way to training or having a break from training, although the teenager occasionally emerges: "Running for a buz back the gym then figuring out its the wrong bus," went one. On the club website she lists some of her favourite things: film – Slumdog Millionaire; group – Black Eyed Peas; colour – lime green.

She hopes to emulate her favourite female gymnast, Shawn Johnson, who won a gold and three silver medals for the US at Beijing, although her coach insists her approach is not to think about medals. "All she has to do is deliver the routine to the best of her ability. Anything else that happens is a bonus," Duffy said.

Tunney has travelled a long way since she made her first journey to the City of Liverpool gymnastics club the year before the Beijing Olympics. She was taken by her mother, Pamela, who was also a gymnast in her youth. Duffy recalls the first time they met: "You could see the excitement in her eyes when she saw what the older girls were doing. She was dying to give it a go."

Her initial interest developed into a strong enthusiasm and determination to compete. "She's the type of child that is willing to try anything and then wants to be the best. She always pushes herself to do the harder routines. She is so determined," said Duffy.

Before she made the Olympic team, Tunney told reporters how she became a gymnast. "My mum did gymnastics when she was little. When she gave that up she went into swimming. She was a really good swimmer. I tried swimming, ballet and everything. I preferred gymnastics. She could see it straight away."

Tunney knows the career of a gymnast is often short but she could last until the Rio de Janeiro Olympics in 2016. "To be honest with you, it depends on how fit I am, how many injuries I have had. See how that goes," she said. "I would like to think that I will stay on. But you never know what will happen in the future."

Tunney has been inspired by her team-mate at the Liverpool club, Beth Tweddle, who is a two-time world champion and captain of the Olympics team. "Because we train with her as well, we see how she trains and how she puts up with the bad days, how she treats the good days. It is good to watch because then we will know how to deal with it too. Obviously, she is good at it as she has won world titles," Tunney said.

City of Liverpool also provided two of the three remaining members of the British artistic gymnastic team, Hannah Whelan and Jennifer Pinches. If they are successful, there is a danger that Liverpool could be as well known for gymnastics as it is for football.

Duffy, who is also head coach at the City of Liverpool, said: "None of us ever thought we could get four girls in the Olympic team. We hope it brings more kids to the club. The young ones are so excited and it makes the prospect of competing at the Olympics so much more realistic for them."